dojox.rpc.JsonRPC Doesn't Deserialize Errors Correctly

Description

This ticket has to do with the switch to dojo/request in 1.8.

In JsonRPC's deserialize function, there is a check to see if the obj passed in has the name 'Error' and if it does, it parses the response text. If the response text has an error property e.g. { "error": "This is an error" }, deserialize would throw a new Error object with the error property's value as the message.

In 1.7, this worked because an Error object (name="Error") would be passed into deserialize.

In 1.8, it doesn't work because a RequestError? object is passed in (name="RequestError?"). A generic "Unable to load ..." message is always returned.